1. Field of the Invention
The present invention generally relates to an image forming device. More specifically, the present invention relates to an image forming device having a rotary type developing unit, and configured to make an image appear using this developing unit.
2. Background Information
Conventionally, in an image forming device that is able to record a color image on a recording paper, a technology of developing an electrostatic latent image is known. This technology uses a rotary type developing unit having a developing machine corresponding to each of the plurality of toner colors including a black color. This kind of image forming device is used as a multifunction device, and has a combination of a plurality of functions of a copying machine, a printer, a fax machine, an internet fax machine, and any function within these functions.
Due to the change in the particle size distribution of toner stored in the developing machine and degradation due to the contact between toners and the like, the quality of the image printed on the recording paper may be deteriorated because the image density of the image printed on the recording paper is lowered, or because of surface fogging, or the like. Especially when a rotary type developing unit is used, since the capacity of the portion that stores toner in the interior of the developing unit is small, the above described problem occurs easily due to the change in the particle size distribution of toner and the like.
An image forming device is disclosed in Japanese Patent Application Publication No. 2000-330379 (disclosed on Nov. 30, 2000), such that in order to resolve this problem, for example, an alternation electric field is impressed between the photosensitive drum and the developing sleeve that conveys toner to a developing region on the photosensitive drum. Thus, toner remaining on the surface of the developing sleeve is attracted to the photosensitive drum, and the developing sleeve is refreshed.
When the developing machine is in a stationary state, toner becomes accumulates in the interior of the developing machine, and the particle size distribution of toner changes. The rotary type developing unit is different from a black and white printer, which is not a rotary type, and by the rotary rotation when color printing, it is possible to mix toner in the interior of the developing machine. Therefore, in a rotary type developing unit, the problem of change in the toner particle size distribution seems to be relatively unlikely to happen.
However, even with a rotary type developing unit, the developing unit does not rotary rotate when printing in black and white. More specifically, when printing in black and white, the rotary type developing unit will perform developing in a state in which the developing machine containing the black toner is stopped at a position opposite the photosensitive drum. Then, even with a rotary type developing unit, a portion of toner in the interior of the developing machine is accumulated, and change in the toner particle size distribution and the like may happen.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved image forming device. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.